Drowning (cont.)

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Does the type of drowning matter?

There have been a variety of theories reported regarding the potential
responses of the body to different drowning situations. Most discuss dry vs. wet
drowning and salt vs. fresh water drowning.

Wet vs. dry drowning

Most drownings are unwitnessed, and the victim is found floating. While only
a small amount of aspirated water is required to cause significant problems with
lung function, it is the prolonged submersion time and lack of breathing that
causes complications due to hypoxemia.

Approximately 10% to 20% of drowning victims have dry drowning with no water
found in the lungs at
autopsy, but even most
wet drowning victims have less than 4cc/kg of water found in their lungs. For a
50 pound child, this amounts to less than 3 ounces of water.

Salt vs. fresh water drowning

In the lung, the breathing tubes (trachea, bronchi, bronchioles) branch into
smaller and smaller segments until they end in an air pocket called an alveolus
(plural alveoli). This is the part of the lung where air and red blood cells in
capillary blood vessels come near enough to allow the transfer of oxygen and
carbon dioxide between the two. Alveoli are covered with a chemical called
surfactant that allows the air pocket to open and close easily when breathing
occurs.

When fresh water enters an alveolus, it destroys the surfactant and causes the alveoli to collapse, unable to open with breathing. A mismatch can develop where blood is pumped to parts of lung where no oxygen is available to be absorbed. This may lead to a decrease in the concentration of oxygen in the blood called a ventilation-perfusion mismatch.

Salt water doesn't destroy surfactan; rather it washes it away and damages
the membrane between the alveolus and the capillary blood vessel. One again, the
body sends blood flow to areas of the lung that aren't able to provide it
oxygen, and hypoxemia occurs.

Regardless of the type of water, lung function is compromised because of the
lack of surfactant, and the effect it has on lung function. In some circumstances,
electrolyte abnormalities may occur with fresh
water drowning.